Fluid annunciators for monitoring malfunctions in engines, compressors and other machines are known in the prior art including piston-type annunciator devices which monitor plural conditions or functions of the machine and indicate any given malfunction at a shut-down point on the machine. Examples of the patented prior art are U.S. Pat. Nos. 3,682,129 and 3,720,182. The device of the latter patent, which is somewhat typical of the known prior art, requires a separate annunciator device or piston indicator for each malfunction point on a machine being monitored. As a result, the tubing and connections for the operating fluid medium, whether air, gas or liquid, is comparatively complex and costly as is the annunciator mechanism proper. In comparison, the present invention provides a much simpler annunciator and shut-down control of the fluid type for compressors, engines and similar machines, in which a single differential area piston and an associated flag and indicia scale is capable of responding to a relatively large number of malfunction points or sensors on a machine being monitored when any of the sensors vents to the atmosphere and thereby provides a leakage of fluid to which the single piston indicator of the invention responds in a unique way. Up to 10 malfunction points can easily be accommodated by the improved annunciator device.
The annunciator is embodied in a simplified and unitary assemblage which includes a piston chamber having plural leakage ports for connection with malfunction sensors on the machine being monitored. The assembly also possesses a flag chamber having an adjacent indicia window for the mounting of malfunction identification indicia specific to a particular machine function, such as pressure, temperature or liquid level. An annunciator flag moving with the single differential area piston coacts with the indicia means to directly indicate the particular malfunction which resulted in the shut down of the machine. The single piston and flag unit also serves to directly activate a control means for the monitored machine such as a multi-way valve or an equivalent electrical control.
Other features and advantages of the invention will become apparent during the course of the following description.